Electrochemical Stability Enhancement of Electrochromic Tungsten Oxide by Self-Assembly of a Phosphonate Protection Layer

The frontier of tungsten oxide nanostructures in electronic applications

Electrochromic (EC) glazing has garnered significant attention recently as a crucial solution for enhancing energy efficiency in future construction and automotive sectors. EC glazing could significantly reduce the energy usage of buildings compared to traditional blinds and glazing. Despite their commercial availability, several challenges remain, including issues with switching time, leakage of electrolytes, production costs, etc. Consequently, these areas demand more attention and further studies. Among inorganic-based EC materials, tungsten oxide nanostructures are essential due to its outstanding advantages such as low voltage demand, high coloration coefficient, large optical modulation range, and stability. This review will summarize the principal design and mechanism of EC device fabrication. It will highlight the current gaps in understanding the mechanism of EC theory, discuss the progress in material development for EC glazing, including various solutions for improving EC materials, and finally, introduce the latest advancements in photo-EC devices that integrate photovoltaic and EC technologies.

Surface modification of rare earth Sm-doped WO3 films through polydopamine for enhanced electrochromic energy storage performance

Electrochromic materials (ECMs) could exhibit reversible color changes upon application of the external electric field, which exhibits huge application prospects in smart windows, energy storage devices, and displays. For the practical application of ECMs, the fast response speed and long cyclic stability are urgent. In this work, the nanoporous Sm-doped WO3 (WSm) films were constructed using hydrothermal technology, then polydopamine (PDA) was modified on the surface of WSm film to obtain the WSm/Px (x = 0.25, 0.5, 1.0, and 2.0) hybrid films. WSm/Px hybrid films displayed high optical contrast and large areal capacitance. In addition, in comparison with WSm film, the WSm/Px hybrid films exhibited faster response speed and better cyclic stability because PDA film enhanced the interface ion transport ability and electrochemical structural stability of the nanoporous WSm film. Notably, the WSm/P1.0 hybrid film displayed the colored/bleached times of 7.4/2.9 s, retained 90.2% of the primitive optical contrast (68.5%) after 5000 electrochromic cycles. Furthermore, the areal capacitance of WSm film could be increased by 224% through the modification of the PDA. Therefore, WSm/Px hybrid films are great prospects for electrochromic energy-saving and storage windows.

On-chip high ion sensitivity electrochromic nanophotonic light modulator

Since the discovery of electrochromism, the prospect of employing various electrochromic materials for smart window glass, variable reflectivity mirrors, and large-area displays has been the main drive for such an intriguing phenomenon. However, with advances in nanofabrication and the emergence of improved electrochromic materials offering reversible large changes in dielectric properties upon electrically induced redox reactions, the application strategies are starting to encompass the field of nanophotonics and nanoplasmonics. Herein, a novel strategy is proposed and demonstrated for offering both ultrahigh light modulation depth and high sensitivity ion detection in a single nanophotonic waveguiding platform. By using WO₃ to ionically-drive dynamic light control via modulating the refractive index and the losses within the waveguide at ±1.5 V, ultrahigh optical modulation depth of 10⁶, rapid response speed of <0.56 s, long cyclic life, and very sensitive Na⁺ ion detection ability in 1 mM-1 M concentration, are achieved within a volume of a few μm³. It is envisioned that our introduction of such a multifunctional electrochromic nanophotonic waveguide platform will stimulate and promote further efforts toward fundamental research on technologically promising on-chip integrated next-generation nanophotonic and nanoplasmonic devices for various niche applications.

Improvement of the froth flotation of LiAlO2 and melilite solid solution via pre-functionalization

In this work froth flotation studies with LiAlO₂ (lithium-containing phase) and Melilite solid solution (gangue phase) are presented. The system was optimized with standard collectors and with compounds so far not applied as collectors. Furthermore, the principle of self-assembled monolayers was introduced to a froth flotation process for the first time resulting in excellent yields and selectivities.

Nanoscale All-Solid-State Plasmochromic Waveguide Nonresonant Modulator

Plasmochromics, the interaction of plasmons with an electrochromic material, have spawned a new class of active plasmonic devices. By introducing electrochromic materials into the plasmon's dielectric environment, plasmons can be actively manipulated. We introduce inorganic WO₃ and ion conducting LiNbO₃ layers as the core materials in a solid-state plasmochromic waveguide (PCWG) to demonstrate light modulation in a nanoplasmonic waveguide. The PCWG takes advantage of the high plasmonic loss at the high field located at the WO₃/Au interface, where the Li⁺ ions are intercalated into a thin WO₃ plasmon modulating layer. Through careful PCWG design, the direction for ion diffusion and plasmon propagation are decoupled, leading to enhanced modulation depth and fast EC switching times. We show that at a bias voltage of 2.5 V, the fabricated PCWG modulator achieves modulation depths as high as 20 and 38 dB for 10 and 20 μm long devices, respectively.

Nanofabrication Techniques in Large-Area Molecular Electronic Devices

The societal impact of the electronics industry is enormous—not to mention how this industry impinges on the global economy. The foreseen limits of the current technology—technical, economic, and sustainability issues—open the door to the search for successor technologies. In this context, molecular electronics has emerged as a promising candidate that, at least in the short-term, will not likely replace our silicon-based electronics, but improve its performance through a nascent hybrid technology. Such technology will take advantage of both the small dimensions of the molecules and new functionalities resulting from the quantum effects that govern the properties at the molecular scale. An optimization of interface engineering and integration of molecules to form densely integrated individually addressable arrays of molecules are two crucial aspects in the molecular electronics field. These challenges should be met to establish the bridge between organic functional materials and hard electronics required for the incorporation of such hybrid technology in the market. In this review, the most advanced methods for fabricating large-area molecular electronic devices are presented, highlighting their advantages and limitations. Special emphasis is focused on bottom-up methodologies for the fabrication of well-ordered and tightly-packed monolayers onto the bottom electrode, followed by a description of the top-contact deposition methods so far used.

Plasmochromic Nanocavity Dynamic Light Color Switching

Static plasmonic metal-insulator-nanohole (MIN) cavities have been shown to create high chromaticity spectral colors for display applications. While on-off switching of said devices has been demonstrated, introducing active control over the spectral color of a single cavity is an ongoing challenge. Electrochromic oxides such as tungsten oxide (WO₃) offer the possibility to tune their refractive index (2.1-1.8) and extinction (0-0.5) upon ion insertion, allowing active control over resonance conditions for MIN based devices. In combination with the dynamic change in the WO₃ layer, the utilization of a plasmonic superstructure allows creation of well-defined spectral reflection of the nanocavity. Here, we employ inorganic, electrochromic WO₃ as the tunable dielectric in a MIN nanocavity, resulting in a theoretically achievable resonance wavelength modulation from 601 to 505 nm, while maintaining 35% of reflectance intensity. Experimental values for the spectral modulation result in a 64 nm shift of peak wavelength with high reproducibility and fast switching speed. Remarkably, the introduced device shows electrochemical stability over 100 switching cycles while most of the intercalated charge can be regained (91.1%), leading to low power consumption (5.6 mW/cm^-2).